Tattoo You is actually nothing more than a collection of outtakes and resurrected rejected song fragments that went back as far as ten years. Some of the music on the album is so old that there are songs that feature Mick Taylor playing instead of Ron Wood. If it weren't for having most of the vocals overdubbed in 1980-81, it would be basically an outtakes compilation.

Other underrated album IMO is Satanic Majesties, but in perspective a lot other artists were doing more adventurous and arguably better albums that year so it depends on the stance one takes. (#1285)
Black and Blue has Hand of fate wich is a quintaessential Stones track. But the album lacks focus. Still think it's underrated somehow. (#3378 and behind compilations)